Refs #30736 -- Added missing versionadded annotations for Storage.get_alternative_name().

Thanks Simon Charette for the report.

docs/howto/custom-file-storage.txt

@@ -99,6 +99,8 @@ and underscores from the original filename, removing everything else.
 
 .. method:: get_alternative_name(file_root, file_ext)
 
+.. versionadded:: 3.0
+
 Returns an alternative filename based on the ``file_root`` and ``file_ext``
 parameters. By default, an underscore plus a random 7 character alphanumeric
 string is appended to the filename before the extension.

docs/ref/files/storage.txt

@@ -107,6 +107,8 @@ The ``Storage`` class
 
     .. method:: get_alternative_name(file_root, file_ext)
 
+        .. versionadded:: 3.0
+
         Returns an alternative filename based on the ``file_root`` and
         ``file_ext`` parameters, an underscore plus a random 7 character
         alphanumeric string is appended to the filename before the extension.